Spray generators

Abstract: An apparatus for generating a liquid spray from two jets of fluid which issue from a pair of opposing nozzles (8,9) and interact, wherein the fluid is supplied to the nozzles (8,9) under fully turbulent conditions such that random variations in the momentum of the fluid as it leaves the nozzles (8,9) occur which results in random variations in the orientation of the resultant spray of liquid drops.

Description: The present invention relates to spray generators of the type in which two opposed jets of liquid impinge on each other and are disrupted to form a curtain of drops. In our earlier patent application, EP 0 331 343 which represents the prior art as referred to in the preamble of claim 1, (US Patent 4,943,007) there is disclosed a spray generator in which two opposed jets of liquid impinge upon each other and are disrupted to form a curtain of liquid drops. Substantially uniform cyclic disturbances are imposed upon the fluid flows at the nozzles, and these cause the spray of droplets to oscillate regularly through an arc. A similar arrangement is disclosed in GB specification 949,954. In both the above spray generators there is included a phased valving device which modulates the flow to one or other of the fluid flow lines leading to the nozzles. Spray generators such as those described in either of the above specifications are satisfactory in operation, but the presence of the phased valving device can give an opportunity for failure, and is a factor in the overall cost of the devices. The spray generator of GB 949,954 provides a limited volume region of spray and is not suitable for use in combination with a vortex gas flow chamber. Specification GB 1,253,221 discloses a liquid spray generator for use with an aerosol spray canister in which a nozzle head has two inlet passages which converge at an acute angle and open into a cylindrical cavity from which there is a single outlet orifice. Jets of liquid issuing from the passages interact within the chamber to form a sheet of fluid which is then formed into a spray of a form which is defined by the shape of the cavity and the outlet orifice. The whole purpose of the device is to produce a liquid spray which has a defined, stable, form. The present invention on the other hand, has for its purposes the production of a spray which varies randomly both in terms of its spatial distribution and droplet sizes. The randomness in the spray is induced by causing the fluid supplied to two opposed nozzles to be supplied in such a way that the momenta of the jets of fluid issuing from the nozzles vary randomly. Specifications DE-C-74301 and FR 1253929-A disclose an apparatus in which a spray of water is formed by the collision of two jets of water which issue from two opposed nozzles. However, in DE-C-74301, the spray is in the form of a downwardly directed conical sheet of droplets. Both the form and direction of the spray of droplets are fixed and determined solely by the shapes of the ends of the nozzles. In FR 1253929-A the spray is indicated to be in the form of droplets projected in a plane perpendicular to the axis on which the opposed jets are aligned. Neither of these specifications discloses or suggests that the flow regime of the water to the nozzles has any part to play in the configuration of the spray produced. According to the present invention there is provided a method for generating a liquid spray of the type in which two opposed jets of liquid impinge upon each other and are disrupted to form a curtain of drops and for flowing a gaseous medium through the curtain of drops to interact therewith, which method comprises flowing a gaseous medium through a chamber with inlet and outlet ports for flow of gaseous medium therethrough, and supplying liquid via liquid flow lines terminating in opposed nozzles within the chamber, from which opposed nozzles the liquid flow emerges in the form of the said opposed jets of liquid which impinge upon one another.and generate a spray of liquid within the chamber, characterised by the combination of features that the chamber is a vortex chamber having at least one tangential inlet port for the gaseous medium and an axial outlet port therefor, and that the liquid is supplied to flow to the nozzles under conditions for which the Reynolds number is greater than 12,000. The invention arises from the realisation that the imposition of variations in the pressure of fluid flowing to each of the nozzles by external valves is not necessary if the fluid flow can be made to be inherently unstable, either by using a pump which produces at least partially turbulent output flow or by operating the device in a region where the fluid flowing in the fluid flow lines does so in an at least partially turbulent fashion, in which case inherently there will be random variations in the fluid flowing to the nozzles, so causing the droplets arising from the interaction of the two jets of fluid from the nozzles to move irregularly through an arc determined by the magnitude of the variations in the momentum of the fluid flowing to the nozzles. The irregular variations in the flow of the fluid may be derived from at least partial turbulence in the flow of the fluid created by a pump associated with the spray generator, or arise by otherwise causing the flow in the fluid flow lines leading to the nozzles to be at least partially turbulent, for example by ensuring that the value of Reynold's Number for the fluid flowing in the fluid flow lines has a value greater than about 12000. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a gas/liquid contactor embodying the invention. Figure 2 is a representation of two stages of a distillation column embodying the invention. Figure 3 is a diagrammatic representation of a multi-stage distillation column embodying the invention. Figure 4 is a diagrammatic representation of another multi-stage distillation column embodying the invention. Figure 5 is a diagrammatic representation of a third form of multi-stage distillation column embodying the invention. Figure 6 is a representation of part of another embodiment of the invention. Figure 7 is a representation of part of yet another embodiment of the invention, and Figure 8 is a representation of another embodiment of the invention. Referring to Figure 1, there is shown a gas/liquid contactor 1 which consists of a cylindrical vortex chamber 2 which has a tangential inlet port 3 for a gaseous phase to be treated in the gas/liquid contactor 1. The vortex chamber 2 has an axial outlet 4 for treated gaseous phase. A liquid phase feed pipe 5 divides into two branches 6 and 7 which enter into the vortex chamber 2 and terminate in two axial opposed nozzles 8 and 9, respectively. A baffle 10 extends across the lower part of the vortex chamber 2 and the portion of the vortex chamber below the baffle 10 forms a sump 11 for the liquid phase 12 which is withdrawn through an outlet 13 and recirculated to the vortex chamber 2 by a pump 14. The pump 14 can be of any convenient type, but it needs to have a capacity such that the fluid flowing in the branches 6 and 7 of the feed pipe 5 has a Reynold's number greater than 12000 so that its flow is at least partially turbulent so causing random variations in the pressures in the feed pipes 6 and 7 and hence the momentum of the fluid as it leaves the nozzles 8 and 9. These random variations in the momentum of the fluid issuing from the nozzles 8 and 9 cause the impacting jets of fluid issuing from the nozzles 8 and 9 to form into a sheet 15 of radially moving droplets which sweeps randomly through an arc which is determined by the size of the random variations in the momentum of the fluid issuing from the nozzles 8 and 9. As described in Specification EP 0 331 343 A, gas entering the vortex chamber 2 via the inlet ports is washed by the sheet 15 of droplets. Droplets are sprayed through the gas vortex to the outer wall of the vortex chamber 2 and drain into the sump 11 through the tubes 16 in the baffle 10. The washed gas, rendered substantially free of liquid leaves the vortex chamber 2 via the axial outlet port 4. Figure 2 shows how a plurality of gas/liquid contactors as described with reference to Figure 1 can be connected in series to form a distillation column. Those ports which are the same as in the gas/liquid contactor already described have the same reference numerals. Feed gaseous phase enters a first stage gas/liquid contactor 20 via a pipe 21. Inside the first stage gas/liquid contactor 20 it meets, and is washed by, a sheet of liquid droplets issuing from nozzles 8 and 9, as before. The liquid from which the droplets are formed is pumped from the sump of a second stage gas/liquid contactor 23 and is supplied to the feed pipes 6 and 7 of the first stage gas/liquid contactor 20 at a pressure such that its flow is at least partially turbulent so as to provide a randomly oscillating sheet of droplets in the manner already described. Liquid draining from the first stage gas/liquid contactor 20 is pumped to a boiler (not shown) by a pump 22 and vapour from the boiler is returned to the feed pipe 21 to the first stage gas/liquid contactor 20. The output vapour from the first stage gas/liquid contactor 20 is fed to the inlet ports of a second stage gas/liquid contactor 23 via an inlet pipe 24. Feed liquor, from a source, not shown, is pumped to nozzles 8 and 9 in the gas/liquid contactor 23 at a pressure such that its flow is at least partially turbulent so that, in the manner already described, a randomly oscillating sheet of droplets is formed in the vortex chamber 2 of the second stage gas/liquid contactor 23. Vapour leaving the second stage gas/liquid contactor 23 through its axial outlet can be either drawn off and condensed, or supplied to a further stage, as required. Figure 3 shows schematically a form of multi-stage distillation column 31 in which the vortex chambers 2 of each stage are contained in an outer vessel 32 which has an inlet port 33 in its base for vapour to be distilled from a boiler 34. The annular passages 35 between the outlet 4 from each stage of the distillation column and the tangential inlet ports, which are not shown, of each succeeding stage of the distillation column 31 act as radial diffusers. The output from the final stage of the distillation column 31 is supplied to a condenser 36 from which purified gas or liquid is withdrawn via an outlet pipe 37. Other liquid from the condenser 36 is supplied to a feed vessel 38 from which it is pumped, under conditions such as to provide a randomly oscillating sheet of drops in the last stage of the distillation column 31. As in the arrangement described with relation to Figure 2 liquid from the sump of a later stage in the distillation column 31 is used to provide the liquid input to the preceding stage. In the case of the first stage, however, liquid drained from its sump is supplied to the boiler 34 and then is added to that drained from the last stage of the distillation column 31. Figure 4 shows, even more schematically another form of multi-stage gas scrubbing column 41 in which liquid from the sump of the vortex chamber 2 of each stage of the column 41 is circulated by a single pump 42 to the jet-forming nozzles 8 and 9 of each stage of the column 41. Figure 5 shows another multi-stage distillation or gas scrubbing column 51 in which the liquid circuit of each stage 52 of the column is entirely independent of that of any other stage 52 of the column 51. Figure 6 shows an annular nozzle arrangement which also has applications as a sprayer for an oil burning furnace or as a water spray for fire fighting purposes. Referring to Figure 6, a pump 61 supplies fluid under turbulent flow conditions to a tube 62 which divides and then comes together as two concentric, but not communicating, tubes 63 and 64. The inner tube 63 projects beyond the end 65 of the outer tube 64 and its end is covered with a flow-reversing cap 66. Thus the opposed annular jets of fluid impinge in the annular region 67 between the upper end 65 of the tube 64 and the lower edge of the flow-reversing cap 66. As before, a sheet of droplets is formed which oscillates with an arc determined by the random variations in the momentum of the jets of liquid emerging from the upper end 65 of the tube 64 and the lower edge of the cap 66 due to the turbulent flow conditions in the tubes 63 and 64. Figure 7 shows another form of opposed nozzle spray head which is considerably easier to manufacture than that shown in Figure 6. Referring to Figure 7, three pipes 71, 72 and 73 respectively, rise from a common manifold 74 to which a fluid to be sprayed is supplied by a high-pressure pump 75. The central pipe 72, projects beyond the ends 71' and 73', respectively, of the pipes 71 and 73 and branches to form a T-shape with two short end pipes 76 and 77 which are of the same diameter as the pipes 71 and 73 and terminate opposite the ends 71' and 73', respectively, of the pipes 71 and 73 and the same distance from them. The alignment between the ends 71', 73' of the pipes 71 and 73 and the ends 76' and 77', respectively of the pipes 76 and 77 is maintained by means of a block of suitable material 78. Thus there is provided a pair of opposed nozzles each of which produces a circular spray of droplets, 79. As before the pump 75 is such as to produce a flow of liquid under conditions such that Reynold's number for the fluid just before it issues from the pipes 71, 73, 76 and 77 is greater than 12,000. The resultant random variations in the flow conditions causes the two sheets of spray 79 to oscillate in a random way, as before. In practice, to ensure the alignment between the ends 71', 73', 76' and 77' of the pipes respective pipes 71, 72, 76 and 77, the T-piece can be fabricated from a solid block which includes suitable drillings with the same centres as those in the alignment block 78 and into the central one of which the pipe 72 fits and into the outer ones of which are inserted short stubs of the same internal diameter as the pipes 71 and 73. As with the previously described embodiments, the nozzle system of Figure 6 or Figure 7 positioned within a vortex chamber 2 provides a gas-liquid contactor. Referring to Figure 8 there is shown, schematically, another form of multi-stage gas treatment column, 81. The apparatus is somewhat similar to that described with reference to Figure 3 and corresponding components bear corresponding reference numerals. In this embodiment of the invention, the sump 12 of the vortex chamber 2 of each stage 82 of the column 81 has an outlet 83 which connects with the upper part of the vortex chamber 2 of the preceding stage 82 of the column 81. The vortex chamber 2 of the last stage 82 of the column 81 has an inlet 84 for a treatment liquid and an axial outlet 85 for a gas which has been subjected to treatment by the treatment liquid. The vortex chamber 2 of the first stage 82 of the column 81, on the other hand, has an axial inlet 86 for the gas to be treated within the column 81 and an outlet 87 for the treatment liquid. In the sump 12 of each vortex chamber 2 there is a weir 88 which controls the level of treatment liquid in the sump 12. Thus, in use, treatment liquid passes through the column 81 in countercurrent to the flow of the gaseous medium to be treated within the column 81. The treatment liquid is circulated continuously in each vortex chamber 2 of the column 81 by means of an associated pump 14 which draws liquid from the sump 12 of the vortex chamber 2 and passes it through pipes 6 and 7 to nozzles 8 and 9, where it forms a spray of drops as before. Again, each pump 14 is such that the treatment liquid is circulated through its associated pipes 6 and 7 and nozzles 8 and 9 under conditions such that Reynold's number exceeds 12,000 and the fully turbulent flow causes random variations in the momentum of the flowing liquid and hence random changes in the orientation of the sheet of droplets formed in each vortex chamber 2 of the column 81.

Claims: A method for generating a liquid spray of the type in which two opposed jets of liquid impinge upon each other and are disrupted to form a curtain of drops and for flowing a gaseous medium through the curtain of drops to interact therewith, which method comprises flowing a gaseous medium through a chamber(2) with inlet(3) and outlet(4) ports for the flow of gaseous medium therethrough, and supplying liquid via liquid flow lines(6,7;63,64;71,76;73,77) terminating in opposed nozzles(8,9;65,66;71',76';73',77') within the chamber(2), from which opposed nozzles(8,9;65,66;71',76';73',77') the liquid flow emerges in the form of the said opposed jets of liquid which impinge upon one another and generate a spray of liquid within the chamber(2), characterised by the combination of features that the chamber(2) is a vortex chamber having at least one tangential inlet port(3) for the gaseous medium and an axial outlet port(4) therefor, and that the liquid is supplied to flow to the nozzles(8,9;65,66;71',76';73',77') under conditions for which the Reynolds number is greater than 12,000. A method according to claim 1, wherein the vortex chamber (2) is cylindrical and the opposed nozzles (8,9;65,66;71',76';73',77') are positioned so as to discharge the liquid axially in the cylindrical vortex chamber (2). A method according to claim 1 or claim 2, further characterised in that there is included a sump (11) for collection of the liquid after it has interacted with the said medium and there is provided means for removing collected liquid (12) from the sump (11). A method according to claim 3, further characterised in that the means for removing the collected liquid (12) from the sump (11) is a pump (14) which also circulates the liquid to the nozzles (8, 9). A method according to any preceding claim, further characterised in that a plurality of vortex chambers (10) each having a pair of opposed nozzles (8, 9) mounted axially therein are arranged sequentially so that the outlet port (4) of one vortex chamber (2) communicates with the inlet port (3) or ports of a succeeding vortex chamber (2). A method according to claim 5, further characterised in that there is provided means for enabling a gas treatment liquid to be passed sequentially through the plurality of vortex chambers (2) countercurrent to the flow through the plurality of vortex chambers (2) of a gaseous medium to be treated in the apparatus. A method according to any preceding claim, further characterised by means for vaporising a liquid medium and supplying the vaporised medium to the vortex chamber (2) thereby to perform a distillation function. A method according to any preceding claim, further characterised in that the nozzles (65,66)) are annular in section and co-axial. A method according to any of claims 1 to 7, further characterised in that a pair of nozzles (71', 76', 73', 77') are positioned side by side and are supplied with liquid from a common supply (72).

Inventors: FORD LIONEL HOUSTON, STAIRMAND JOHN WILLIAM, FORD, LIONEL HOUSTON, STAIRMAND, JOHN WILLIAM
Applicants: ACCENTUS PLC
Application year: 1994
Main classification: B05B1
IPC codes: B05B1, B01F3, B05B7